Roll No.__________________
09 August, 2018
Sarhad University, Peshawar
(Distance Education)
Paper
: Electric Machines - II-ELC315
Examination: Final, Spring-2018
Total Marks: 70, Passing Marks (35)
Time Allowed : 3 hours
NOTE: Question No.1 is Compulsory. Attempt any four questions from the rest. All questions carry equal marks.
Phones and other Electronic Gadgets are not allowed.
Q.1
i.
ii.
iii.
iv.
v.
vi.
vii.
viii.
ix.
x.
a) chose the correct answer
A single phase induction motor employs ……………… rotor
Squirrel cage
b) wound
c) both
d) none
An alternator is sometimes called …………………. Generator
Synchronous b) asynchronous c) either a & b d) none
The field winding of an alternator is ……………………. excited
a) D.C
b) A.C
c) Both a & b
d) None
The Frequency of an EMF generated in an 8-pole alternator running at 900 RPM is …………………
a) 50 Hz
b) 60 Hz
c) 120 Hz
d) 100 Hz
When a 3-Phase induction motor is at no load the slip is ………………….
a) 1
b) 0.5
c) 0
d) Maximum
i.
ii.
iii.
iv.
v.
b) Fill in the blanks
The stator of a 3 phase induction motor produces ……………..Magnetic field.
The primary and secondary of a transformer are ……………………….Coupled.
A transformer is a efficient device because it is ……………………..
3-phase wound motors are also called ……………………..motor.
Most of the single phase induction motor are ………………….pole machine.
Q.2
Discuss the characteristics and application of synchronous motors.
Q.3
Draw equivalent circuit of transformer on no load, and its phasor diagram.
Q.4
Derive formula for induction motor torque i.e. shaft torque and rotor torque?
Q.5
Explain synchronous impedance method of an alternator.
Q.6
Explain universal motor in detail (construction, operation & characteristics).
Q.7
Explain the operation of 3 phase induction motor and the effect of load on the motor.
Q.8
Write short notes on any TWO
i.
Stepper motor
ii.
Write four conditions for parallel operation
iii. Voltage regulation of Alternator.
Electric Machines - II-ELC315-Spring-2018
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